1. Field of the Invention
The present invention relates to an image forming apparatus, to an image forming method and to an image storage medium, particularly to an image forming apparatus, an image forming method and an image storage medium useful for forming an image on a board such as a printed wiring board or a flat panel display board.
2. Description of the Related Art
A surface exposure apparatus using a mask has been widely used as an apparatus for forming a predetermined pattern on a printed wiring board (hereinafter referred to as “PWB”), or on a flat panel display (hereinafter referred to as “FPD”) board.
However, high resolution of a pattern (wiring pattern) formed on a PWB is needed as high density mounting of components increases, and a problem arises insofar that a forming position can be displaced due to expansion and contraction of the mask, or to expansion and contraction of the board generated in a pressing process performed mainly in the heated state. For example, since, in the case of a multi-layered printed wiring board, alignment between a hole made in the board, such as a through hole, and the pattern of each layer, can not be performed with high accuracy, the inability to achieve a high density on a PWB becomes a problem.
In the case of FPDs, increases in the sizes of boards have been made in the interest of high productivity, and a problem has arisen that a lithography position can be displaced as a result of an increase in the degree of expansion and contraction of the board before and after heat treatment, or as a result of the expansion and contraction of the mask itself. For example, in forming a color filter pattern, the displacement of each color of R (red), G (green), and B (blue) becomes a problem.
Among technologies designed to solve the kind of problem mentioned above, for example, as disclosed in Japanese Patent No. 300020, a technology has existed in which the pattern is directly formed on a recording, medium without the use of a mask (hereinafter referred to as “first related art”).
According to the first related art, displacement of the forming position can be corrected by controlling a frequency of a forming clock pulse, a feeding speed of a forming stage, or a starting time of forming.
Further, for example, as disclosed in Japanese Patent Application Laid-Open No. 2000-122303, a technology has also existed in which a PWB is moved in a sub-scanning direction while a light beam is scanned in a main scanning direction, and multiple surface forming patterns are formed on the PWB by modulating the light beam on the basis of lithography data; a technology has also been used in which surface forming positional information on the PWB is measured, and displacement of the forming position corrected on the basis of the surface forming positional information obtained at the time that vector data is converted into bit map data (hereinafter referred to as “second related art”).
However, because the degree of expansion and contraction of a board such as a PWB or a FPD board is not isotropic, boards expand and contract not only into the shape of a rectangle or a parallelogram, but also into arbitrary shapes. Therefore, in the first related art, a problem has arisen that, as the high resolution of the forming pattern increases, displacement of forming positions can not be sufficiently corrected.
In the second related art, only the positional information of the surface forming pattern is corrected, and accordingly there has also been a problem that it has not been possible to cope with strains caused by the generation of an arbitrary shape of a board.
In view of the foregoing, the invention provides an image forming apparatus, an image forming method and an image storage medium that can correct with a high degree of accuracy displacement of a forming position of an image even when the recording medium is strained into an arbitrary shape.